1. Field of the Invention
The present invention relates to an implant for a bone connector used for connecting bones.
2. Description of the Related Art
When connecting bones such as thoracic vertebrae or lumbar vertebrae, the following method has been conventionally employed. A first implant 3 is screwed into centrum 1 such as the thoracic vertebra and the lumbar vertebra. A second implant 4 is screwed into centrum 2. A connecting rod 5 connects the first implant 3 to the second implant 4 as shown in FIG. 1.
The first implant 3 includes a screw portion and a head portion. The screw portion is screwed into centrum and the head portion with a large diameter has a rod engaging groove. Also, the second implant 4 includes the same conformation. Since end portions of the connecting rod 5 are fixed to the rod engaging groove of the first implant 3 and that of the second implant 4 respectively, the connecting rod 5 is integrally fixed to the first implant 3 and the second implant 4 and accordingly a bone connector is formed.
Further, an implant 9 is screwed into centrum 10 separating from the centrum 1 and the centrum 2 for hooking one end of a connecting member 7 such as an artificial ligament. A hook portion 9F is provided on an upper portion of the implant 9, and one end portion of the connecting member 7 is hooked over the hook portion 9F. Another end portion of the connecting member 7 is hooked over a hook portion 5F provided on one top end (the side engaged the first implant 3) of the connection rod 5.
Also, instead of using the connecting rod 5, the connecting member 7 may be used for connecting a first implant to a second implant. A first implant having a hook portion is screwed into the centrum 1, a second implant having a hook portion is screwed into the centrum 2, and both end portions of the connecting member 7 are hooked over the hook portion of the first implant and that of the second implant respectively.
According to the above-described method screwing the implant for a bone connector into the centrum for fixing a positional relation between vertebrae, it is necessary to precisely screw the implant into the centrum without damaging other portion. This method requires high technique and a burden of the centrum becomes large, because the implant is screwed into centrum.